Barge Unloading Facility Build

[Espeefan]

Jim, have you considered using a chain drive, driven by the servo? Continuous operation, in either direction, no tracking issues, and you could probably mount a cam to the chain to engage a dog on the barge, to pull or push where you want it. Might be a little more reliable and simpler. It may not be the scale look you are after though..? There is some pretty small and light chain you could use, with sprockets designed to bolt right to a servo output shaft. Couldn't be easier. Just use a simple method (idler sprocket) to keep your chain tight, and you're good to go!

http://www.servocity.com/html/sprockets___chain.html